This invention pertains to vehicular transport and, more particularly, to methods and apparatus for the guidance and switching of vehicles.
Vehicle guidance is an important part of any transportation system and for centuries a sequence of new schemes have been devised to guide or steer a vehicle. For example, conventional railroads use conical wheels and a solid axle to provide guidance, while a flange on the wheel provides backup guidance in case an exceptionally strong force is required. Automobiles use steered wheels which depend upon traction with a road to provide guidance. Air cushion vehicles use air pressure for both vertical suspension and horizontal guidance. Magnet levitation (maglev) vehicles utilize magnetic forces for both suspension and guidance. Some transportation systems use rubber tired wheels for suspension with additional guidance wheels that interact with special guidance rails to control the direction of vehicle travel. Some of the more recent patents on these and related topics are: U.S. Pat. Nos. 3,628,462; 3,768,417; 3,858,521; 3,927,735; 4,061,089; 4,522,128; and 5,277,124.
All guidance systems must have means to choose between alternate directions of travel. Automobiles use steered wheels to control lateral motion, a method that works well when traction is good but works poorly in wet or icy conditions when traction is bad. Conventional trains use switches with mechanically movable rails, a system that works well in some applications but takes several seconds to activate and is prone to maintenance problems. Magnetic or air cushion suspended vehicles use switches that require motion of large sections of a guideway. Accordingly, these latter systems have the same disadvantages as trains, in addition to high cost. Although the art has additionally proposed certain uses of magnetic forces to guide magnetically suspended vehicles (e.g., as described in U.S. Pat. Nos. 3,768,417; 3,858,52 and 3,927,735), these generally do not have broad application.
In order to allow vehicles to operate with headways of 1 second or less, systems for automated material handling or personal rapid transit have used lateral guidance wheels with mechanically movable parts on the vehicle to initiate switching; this is exemplified in U.S. Pat. Nos. 4,061,089; 4,522,128; 5,277,124. These systems all depend upon movable wheels that engage either a left or a right guidance rail according to the preferred direction of travel. These guidance and switching means tend to cause substantial mechanical drag forces and, require considerable maintenance.
Since all guidance systems have both strengths and weaknesses, there has been a continual search for new methods of achieving guidance.
In view of the foregoing, an object of the invention is to provide improved methods and apparatus for vehicle guidance and switching. A more particular object of the invention is to provide such methods and apparatus as can be applied to all types of vehicles, regardless of the mechanisms by which they are suspended and/or steered.
A further object of the invention is to provide such methods and apparatus as can be applied to guidance of wheeled "road" vehicles, such as automobiles, buses and trucks. A related object is to provide such methods and apparatus for "track" vehicles, such as trains, trolleys, personal rapid transits vehicles and baggage-carrying vehicles.
A still further object of the invention is to provide such methods and apparatus as require few, if any, moveable mechanical guidance components and, therefore, which can be applied in low headway applications, such as personal rapid transit.
Yet still another object of the invention is to provide such methods and apparatus as can be utilized to guide and switch vehicles on friction, as well non-friction, surfaces.
These and other objects of the invention are evident in the drawings and in the description that follows.